<!DOCTYPE html>
<html>
<head>
	<meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> 
	<title>模板标签</title>
	<style type="text/css">
	
	ul {
		list-style: none;
		margin: 10px 0;
		border: 1px dotted #aaa;
	}

	li{
		widows: 300px;
		padding: 5px 0;
	}

    </style>
</head>
<body>
	<div class="container">
		<h1>模板标签</h1>
		<div id="box">
			
		</div>
	</div>
<script src="https://cdn.bootcss.com/decimal.js/10.2.0/decimal.min.js"></script>

<script src="https://cdn.staticfile.org/jquery/3.2.0/jquery.js"></script>
<script type="text/javascript">
//https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/Math/floor
// Closure
(function(){

	/**
	 * Decimal adjustment of a number.
	 *
	 * @param	{String}	type	The type of adjustment.
	 * @param	{Number}	value	The number.
	 * @param	{Integer}	exp		The exponent (the 10 logarithm of the adjustment base).
	 * @returns	{Number}			The adjusted value.
	 */
	function decimalAdjust(type, value, exp) {
		// If the exp is undefined or zero...
		if (typeof exp === 'undefined' || +exp === 0) {
			return Math[type](value);
		}
		value = +value;
		exp = +exp;
		// If the value is not a number or the exp is not an integer...
		if (isNaN(value) || !(typeof exp === 'number' && exp % 1 === 0)) {
			return NaN;
		}
		// Shift
		value = value.toString().split('e');
		value = Math[type](+(value[0] + 'e' + (value[1] ? (+value[1] - exp) : -exp)));
		// Shift back
		value = value.toString().split('e');
		return +(value[0] + 'e' + (value[1] ? (+value[1] + exp) : exp));
	}

	// Decimal round
	if (!Math.round10) {
		Math.round10 = function(value, exp) {
			return decimalAdjust('round', value, exp);
		};
	}
	// Decimal floor
	if (!Math.floor10) {
		Math.floor10 = function(value, exp) {
			return decimalAdjust('floor', value, exp);
		};
	}
	// Decimal ceil
	if (!Math.ceil10) {
		Math.ceil10 = function(value, exp) {
			return decimalAdjust('ceil', value, exp);
		};
	}

})();

// -1 10^-1 小数点后1位
console.log(Math.round10(55.5512, -1)); // 55.6
console.log(Math.round10(55.54926, -1)); // 55.5

console.log('-----------------------\n')

// -2 保留2位小数  2 变为 10^2 四舍五入
console.log(Math.round10(55.5512, -2)); // 55.6
console.log(Math.round10(55.54926, -3)); // 55.5
console.log(Math.round10(55.54926, 2)); // 55.5
console.log(Math.round10(45.54926, 2)); // 55.5

</script>
</body>
</html>

